Efficacious antonyms

What is the opposite word for Efficacious?

Use filters to view other words, we have 35 antonyms for efficacious.
Antonyms for efficacious
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Efficacious Thesaurus
Definitions of Efficacious
Efficacious Synonyms
Nearby Words
efficacy, efficaciousness, efficaciously
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Opposite words of efficacious
Image search results for Efficacious
ability, competence, aptitude ability, competence, aptitude ability, competence, aptitude ability, competence, aptitude ability, competence, aptitude
Cite this Source
Antonyms for Efficacious. (2016). Retrieved 2026, July 19, from https://thesaurus.plus/antonyms/efficacious
Antonyms for Efficacious. N.p., 2016. Web. 19 Jul. 2026. <https://thesaurus.plus/antonyms/efficacious>.
Antonyms for Efficacious. 2016. Accessed July 19, 2026. https://thesaurus.plus/antonyms/efficacious.